A Moving Picture Experts Group (MPEG) Media transport Technology (MMT), which is one of technologies of transmitting information in a multimedia system, transmits and receives information using an Automatic Repeat Request (ARQ) method.
A transmitting entity in the ARQ method of the conventional MMT system decides whether to support the ARQ for each Asset, however it does not notify a receiving entity of whether to support the ARQ. In this case, a problem may occur, in which the receiving entity may not know whether or not to receive a reply when lost packets are requested again, and for a seamless service, the transmitting entity or an ARQ server has to store MMT packets for all assets owned by themselves for a predetermined time or more. Here, the transmitting entity may perform an operation of the ARQ server, which stores and transmits a retransmission packet.
In addition, when the ARQ request is made by the transmitting entity, the MMT ARQ message may be made by only one kind of combination of Packet_ID and PACKET_SEQUENCE_NUM and the retransmission request may be made by the MMT ARQ message, and which means that the retransmission request is possible only in a packet unit. However, the MMT system includes not only MMT packets but also various levels of media units, such as a Media Processing Unit (MPU), a Media Fragments Unit (MFU), a sample and the like, and when the receiving entity may request a desired level of media unit, a more useful data recovery is possible.
FIG. 1 illustrates an example of applying an ARQ method in a conventional MMT system.
Referring to FIG. 1, a transmitting entity 100 determines a retransmission delay time (Dt) value (indicated by reference numeral 101), transmits an ARQ Configuration (AC) message including information related to the determined Dt value to a receiving entity 200 (indicated by reference numeral 103). Thereafter, when the receiving entity 200 successfully receives a packet N−1 and a packet N+1, and fails to receive a packet N (indicated by reference numerals 105 to 109), the receiving entity 200 calculates an arrival deadline time (Arrival_Deadline) value (indicated by reference numeral 109) and does not perform an additional operation for receiving a packet to the extent of the calculated Arrival_Deadline value. Here, the Arrival_Deadline value is calculated based on the Dt value and an ARQ feedback delay time (Df) value.
In addition, the receiving entity 200 transmits, to the transmitting entity 100, an ARQ feedback (AF) message requesting retransmission of the packet N which has not been received (indicated by reference numeral 113). Here, the AF message includes information related to the Arrival_Deadline value and information related to ARQ feedback time stamp.
The transmitting entity 100 checks the Df value, the Round Trip Time (RTT) value, and information related to the Arrival_Deadline value from the received AF message (indicated by reference numerals 115 to 119), and determines whether the RTT value is smaller than the Arrival_Deadline value (indicated by reference numeral 121). In addition, when the RTT value is smaller than the Arrival_Deadline value, the transmitting entity 100 may retransmit the packet N (indicated by reference numeral 122), and when the value of the RTT is not smaller than the Arrival_Deadline value, the transmitting entity 100 is in a standby state until the Arrival_Deadline value is terminated.
That is, the conventional ARQ method described in FIG. 1 is a scheme where the receiving entity 200 transmits the Arrival_Deadline value to the transmitting entity 100, and when a packet for which the retransmission is requested is not transmitted to the final receiving entity 200 to the extent of the Arrival_Deadline value, the transmitting entity 100 gives up a response transmission itself. However, since the Arrival_Deadline value may be known when the receiving entity 200 checks all of the receiving packets and recovery media, there is a problem of consuming a large amount of time and resources in order for the receiving entity 200 to derive the Arrival_Deadline value. In addition, when the transmitting entity 100 gives up the response transmission, a problem may occur in that the receiving entity 200 does not recognize thereof and has to wait until the Arrival_Deadline value is terminated.
Thus, since the conventional MMT system may not provide the valid period information of Asset Delivery Characteristic (ADC) information representing individual transmission characteristic values of each of the Assets, a scheme for solving this problem is required. On the other hand, MMT media data, which is transmitted from a specific transmitting entity to a receiving entity, is often transmitted by combining Assets having higher relevance and grouping the same in a bundle unit as well as in one asset. Therefore, the network may easily manage Bundle Delivery Characteristics (BDC) information in the bundle unit, rather than controlling and managing the Asset unit. However, in the conventional MMT system, ADC information is provided in the Asset unit which corresponds to each individual media, and in this case, since the discovery and management of ADC information are performed in the Asset units, from the point of view of a network entity for the server/MMT (MMT aware network entity: MANE), unnecessary information may be provided. In addition, there is a means for providing the importance on data to be transmitted at each separate packet level, and priority information thereof, however not only bundle information which is information on the bundle of Assets at a media level which has a proper relationship but also relative priority information between bundles within the bundle, Assets within the bundle, and Assets are not given.